Detergent manufacturers constantly seek to improve their product performance, process flexibility and more recently, the environmental impact or sustainability of their products. It has therefore been a desire for some time to produce and sell compact formulae that use less water and require less packaging whilst maintaining, and preferably improving, product performance.
Anionic surfactants, especially sulphated surfactants are pre-processed, prior to inclusion into a product composition, into a processable surfactant concentrate. Typically water is used to control the viscosity of the concentrate. However, this presents a problem when formulating for compact formulae as discussed above, as it is the general aim to reduce the water content of the product composition. This problem is particularly relevant when the product composition is to be sold as a unit dose of a liquid composition within a water-soluble or dispersible pouch. In this latter situation, the product is not stable when the composition comprises greater than 20% water. Hence it is the aim of the formulator, to reduce the level of water being brought into the final product through the raw materials.
Furthermore, when manufacturing sulphated surfactant concentrates it is essential that the surfactant concentrate can be processed, shipped, stored, pumped and ultimately used in its designated application throughout the life time of the concentrate. Typical issues that arise are either, a viscosity of the concentrate that is too high to process effectively or the instability of its key active, an anionic sulphated surfactant, over time. If not stabilised, the sulphated anionic surfactant either physically or chemically disintegrates into its constituent parts or other degradation products. It is essential therefore, that the concentrate firstly provides sufficient stability over time from point of making, until the point of its application. This stability must be achievable at all temperatures at which the surfactant concentrate is processed, shipped, stored, pumped and applied. Secondly, the surfactant concentrate must also have a pumpable viscosity throughout its lifetime.
EP 507 402 (Unilever) relates to a continuous process for preparing a liquid detergent composition comprising anionic surfactant and nonionic surfactant. The detergent composition has a low water content. In this process, equimolar amounts of neutralizing agent and a liquid acid precursor of the anionic surfactant are blended simultaneously in the presence of nonionic surfactant. EP 507 402 describes the presence of fatty acid, but requires that the fatty acid be present in the free acid form.
EP 1 272 605 (Unilever) relates to a continuous process for preparing a fluid detergent composition comprising anionic surfactant. Said process comprises mixing, in a first mixer, an anionic surfactant precursor with sufficient neutralization agent to achieve 25-75% neutralization of the anionic surfactant precursor, then mixing the result with sufficient further neutralization agent in a second mixer to achieve 100% neutralization. EP 1 272 605 mentions the presence of soap, meaning the salt thereof, and describes the benefits of using a salt in this context.
It is the object of the present invention to develop an anionic sulphated surfactant concentrate that does not require the use of water for process ability and an efficient, continuous process for making said concentrate. It has been a further aim of the present invention to develop a highly efficient anionic sulphated surfactant concentrate wherein the high efficiency of the surfactant means that less surfactant is required in the finished product. Such a highly efficient surfactant system permits formula flexibility, reduces the environmental impact and irritancy of the concentrate or final product composition.